1. Field of the Invention
This invention relates to a plastic cap having a low cap height and a reduced resin weight as well as excellent sealing reliability, easy openability, and tamper-evidence.
2. Prior Art
Because resin caps can be produced by integral molding and have excellent moldability and flexibility, they can be fixed to a mouth portion of a container by a capping operation, and have been used widely in various forms.
Various resin caps having excellent openability which have excellent sealability, and can be removed easily from a mouth portion of the container without using a tool have been proposed. For example, Japanese Laid-Open Patent Publication No. 58719/1997 describes the structure of a synthetic resin cap comprising a mouth portion of a bottle, two circumferential grooves provided along its outer peripheral portion and the cap mounted in engagement with the top of the mouth portion of the bottle and the inner surface of the mouth of the bottle. This cap is a one-piece cap composed of an upper closure, a tamper-evident band and a side score portion which connects the lower end of the upper closure portion to the upper end of the tamper-evident band on a circumference.
The above prior art is significant because it provides a plastic cap openable by a hand without any particular tool such as a cap opener, and having a function of preventing a fraudulent act. However, two-staged engagement jaw portions are present for holding a tamper-evident property and for holding resealing on the outer circumference of a container, and therefore two-staged protrusion portions exist on the cap side. Because of such portions, there is an inconvenience that the cap height becomes high, and the resin weights of the mouth portion of the container and the cap become high.